1. GIS Tools for Watershed Delineation Public Policy Perspectives Teaching Public Policy in the Earth Sciences April 21, 2006 Gary Coutu Department of Geography and Planning West Chester University

2. Contents Watershed Perspectives in Policy Environmental Mandates GIS Data for Watershed Characterization Tools for Watershed Delineation and Analysis Examples for Classroom and Research Issues

3. Watershed Perspectives in Policy Watershed- EPA approach for managing land and water quality TMDL: Total Maximum Daily Load 303d List of Impaired Waters EPA Support- Data, GIS tools and Models Issue- National data sets versus local information and data Many Agencies support data and model development for environmental assessment, management and mitigation

4. Environmental Perspectives TMDL (Total Maximum Daily Load): calculation of the maximum amount of a pollutant that a waterbody can receive and still meet water quality standards. Established in the Clean Water Act, section 303. Section 303(d) of the Clean Water Act Under section 303(d) of the 1972 Clean Water Act, states, territories, and authorized tribes are required to develop lists of impaired waters. These impaired waters do not meet water quality standards that states, territories, and authorized tribes have set for them, even after point sources of pollution have installed the minimum required levels of pollution control technology. The law requires that these jurisdictions establish priority rankings for waters on the lists and develop TMDLs for these waters. http://www.epa.gov/owow/tmdl/overviewfs.html

5. Total Maximum Daily Loads on the Web TMDLs and the 303d list are developed concurrently. EPA publishes information and local links on their web site. Reporting and analysis: Based upon a large set of spatial data for watershed and stream locations. Most of this data developed by USGS USGS Data: Hydrologic Units National Hydrography Dataset Stream Gauges

6. GIS Data for Watershed Characterization DEM: Digital Elevation Model. Grid of elevation points (each cell has an elevation value HUs: Hydrologic Units. Nested watershed units NHD: National Hydrography Dataset. Networked streams and features for modeling (includes human and natural waterways, damns, ponds, etc.) USGS Gauging Station Data

7. Hydrologic Unit Maps Regions (21 major geographic areas) Sub-regions (222 subregions) Accounting units (352 hydrologic units) Cataloging units (2150 SubBasin) Hydrologic Unit Code (HUC): Consists of two to eight digits. The 6 digit accounting units and the 8 digit cataloguing units are generally referred to as basin and sub- basin. Two new levels, watershed and subwatershed, are under development. Watershed address system DescriptionProper NameAddress RegionOhio River05 SubregionWabash/Patoka/White Riv0512 BasinWabash River051201 SubheadVermilion River05120109 WatershedNorth Fork Vermilion0512010909 Subwatershed Lake Vermilion051201090905 Represent watershed areas used for policy and environmental analysis/management

8. Nested Hydrologic Units All Federal and State Agencies use this nested hierarchy 0204 (Delaware) 020402 (Lower Delaware) 02040205 (Brandywine-Christiana) 0204020535 (Upper Reach Brandywine Creek) Sample Watershed for this Presentation (560 Acres)

9. National Hydrography Datasests GIS layers (ArcGIS Geodatabase) stored as a Microsoft Access Database

10. USGS Gauging Stations: Real-time Data

11. Tools for Watershed Delineation and Analysis

12. BASINS: Water Quality Model Better Assessment Science Integrating Point & Nonpoint Sources: Environmental analysis system integrating GIS, national watershed data, and environmental assessment and modeling tools.

13. Watershed Delineation Process Foundation of watershed analysis in the classroom Steps: –Fill Sinks –Flow direction –Flow Accumulation –Define Watershed –Analysis

14. Delineation Process: Fill Sinks Sink: Cells of the DEM that do not drain Issue: Watershed commands won’t work Teaching: Students are exploring limitations of modeling Sinks

15. Delineation Process: Flow Direction/Accumulation Flow Direction: Assigns Direction of flow from cell to next lowest elevation (D-8 algorithm) Flow Accumulation: Total number of cells flowing into that cell (Can calculate streams and ridges) 013 024 006 3264128 16X1 842

16. Delineation Process: Use/Interpretation Flow Accumulation: Generate Streams Flow Direction: Identify Water Flow Slope

17. Delineation Process: Watershed Pour point at Stream confluence Watersheds represent the drainage area to a point (known as the “pour point”.) Delineation tools allow a user to define the watershed for a selected drainage.

18. Watershed Delineation: Use/Interpretation DEMContours Steep Slopes Data sets can be clipped for local watershed areas for analysis

19. Stream Network Modeling Stream networks from the National Hydrography Dataset can be included in watershed analysis. Stream, watershed and land use data are used to explore environmental impact. Downstream Impact Commercial Site ImpactWatershed Parcels

20. Land use/Water Quality TypeAcres Open Water1 Low Intensity Residential157 High Intesity Residential9 Commercial14 Deciduous Forest203 Evergreen Forest4 Mixed Forest76 Pasture Hay89 Row Crops4 Land use within a watershed can be isolated and quantified:

21. Watershed Characterization Students perform this analysis and tasks as part of a watershed study. Could be combined with field work.

22. Example Issue: DEM Resolution and Stream Layer Accuracy 1.DEM Resolution (10 meter vs 30 meter) 2.DEM Generated Stream Accuracy 3.Stream confluence and DEM confluence mis- match Stream 30m DEM 10m DEM Stream Confluence Student Experience: 1.Resolution/Scale Issues 2.Stream Map Generation 3.Field Data Integration 4.Context of Modeling

23. Web Sites EPA Surf Your Watershed: http://www.epa.gov/surf/ EPA TMDL: http://www.epa.gov/owow/tmdl/intro.html EPA BASINS: http://www.epa.gov/OST/BASINS/ USGS DEM: http://www.usgsdigital.com/Elevation.htm USGS Stream Gauges: http://water.usgs.gov/nsip/ National Hydrography Data: http://nhd.usgs.gov

24. Contact Gary Coutu Department of Geography and Planning West Chester University West Chester, Pennsylvania Email: gcoutu@wcupa.edu